Brake problems on a 156

[L4OMEO]

Hi all

Need some advice on brake problems. A few months back I installed some DBA slotted rotors along with some Ferodo DS Performance pads and braided lines, and some problems have since developed.

- brakes start to 'chirp' when not being applied once warmed up (haven't noticed this since a long country trip last weekend though, & I did use copper grease)
- brakes squeal at lower speeds when being applied once warmed up
- brakes groan when applied when hot
- actual braking power is less than the previous stand/worn set-up, and the car pulls to one side under hard braking when hot
- when giving the pedal a quick stab there's a bit of a 'clunk' as the brakes bite
- handbrake now needs to be pulled up much further to work (was fine after installation, travel has lengthened since)

I'm getting it serviced shortly and will probably get this sorted then, but for my own understanding (and to help minimise the time the mechanics spend diagnosing) I'd like to actually know what's going on here. It seems to me that there could be a number of causes here, although maybe there's one problem creating many symptoms (a faulty caliper perhaps?). Any input on any of these issues would be welcomed.

Cheers
Rory

[L4OMEO]

Just remembered one further symptom - after the car has been parked for a couple of days one of the calipers seems to be sticking on (ie one of the rotors is still clamped, releases with a bit of a jolt as you start to move. Feels like one of the fronts).

Thanks again
Rory

[Craig C]

Have you tried braking with just the handbrake to check whether it is a front or rear brakes problem?

[wankski]

from what u've described it's pretty obvious you have a sticking piston, which will cause the scraping when off the brakes, as well as skewed braking under pressure...

who installed the rotors and pads?

the cold temp braking is what i would expect of fedoro performance items,... for road use, always use OEM.

As for handbrake could be a few things... have u checked as above with rear handbrake only braking? if only one side of that sticks too, i'd guess one of the two L/R cables have popped, or some other issue....

there could be a range of other 'muppet' issues that it may be (i.e. dumbass installer) lets hope not...

normally scraping while not using brakes is simply the dust cover getting bend and fouling on the rotor, but doesn't sound lke it in this case...

good luck.

[L4OMEO]

Hi guys

Thanks for the replies.

Craig - haven't tried the handbrake in that manner, might be a few days before I drive it again but might see if that can help isolate which end is having the problems.

Wankski - a sticking piston was my initial thought as it explains more than one of the symptoms.

there could be a range of other 'muppet' issues that it may be (i.e. dumbass installer)

That's quite a likely possibility since it was me  And a more mechanically qualified friend I should add. I'm not yet convinced it's a direct result of something we've done but I'm not in denial either. We were pretty confident in our reassembly, but it did take a long time to get a good pedal so maybe something wasn't right even then.

Re: the Ferodo pads - I chose the DS Performance on the basis that they were a slight step up from OEM and would therefore avoid the compromises a more performance-oriented like the Ferodo DS2500 pad would bring. I've never read of anyone having issues with this pad in a road-car application, and since none of my problems have been when cold this seems to substantiate this rationale. The issues are all when the pads are at normal operating temperature or higher, which is surprising as it's in this window I expected an improvement over OEM. This makes me think that some other problem in the brake system (ie like a sticking caliper) might be playing a part.

Having said that, could it be that I've chosen a compund of pad which simply doesn't work well with my choice of cailper?

Anyway, will get it all checked in a couple of weeks by people who know what they're doing    Thanks again for your help, any further feedback still very welcome.

Cheers guys

Rory
Dumbass Installer

[wankski]

haha, d'oh! i didn't mean that, that way....( i didn't go thru bone head causes for that reason...lol)

pads vs caliper -  if the pad fit without requiring modification to fit, then its fine and not to do with the caliper... assuming u didn't wear in the pads after new, it's likely a pad/rotor issue...

if the pads are brand new, with these performance types (dunno about fedoro in particular) there is often an inital scrub layer to bed in the rotor, so it may simply be u're still on that... since it's been a couple of months, perhaps u're looking at a glazing issue (hence causing the low speed squealing)

check to see if the backing plates are bent at all, and at least u can eliminate that...

then test handbrake as described to at least assess where that's at...

question, since it was you, how did you change the rear pads? as in retract the piston in the caliper?

[L4OMEO]

Sure you meant it, you rude b****d!!!! 

Pads were brand new and it's been predominantly city driving since they went in, so glazing could be an issue. That's why I gave them a workout in the country to try and get some life back into them, and it was during this that the stopping power fell away as they heated up and the car veered to one side. If the pads are glazed, will a good strop generally fix them or do they need to be removed and the surfaces buffed somehow?

Could be on to something re: the rear calipers. My friend did these and he did have some problems retracting the calipers. Have to be honest, not sure how he got it done in the end so there could well be a problem there. Have also noticed that the rears have always generated a lot more brake dust than the fronts which would tend to support a problem at that end (although, these were installed a year ago before I bought the car, not sure what they are but suspect something cheap which might explain the dust).

Thanks again for your help wankski
Rory

[wankski]

glazing - depends... some pads have a scrub layer, which is designed to scrub the disc hard during intial break-in of the interface... so yes, while hard braking may help, it will not be as good as the original interface if the scrub layer is gone... harder higher temp 'sport' compound is far more likely to glaze at low temp short use due to the compound.


rear brakes - i ask as they, unlike the fronts, require a thread in tool to reverse the threaded rear pistons. Attempting to jury rig it, or worse, use a vice or similar as you would with the fronts will no doubt damage them.

A specialist reversing (RHT) tool with correct piston interface is required for the rear calipers. If you apply too much pressure on the threaded piston with a vice or c clamp or similar, u could easily damage the soft aluminium causing deep gouging or at least a damaged thread, which could easily be causing the sticking piston problem.

or it could be something else... hard to say without having a look, or having done the job on your car ...mere speculation at this point...

so we can assume in the absence of proof to the contrary, you did an excellent job!   

[L4OMEO]

so we can assume in the absence of proof to the contrary, you did an excellent job!

Err ... unfortunately proof to the contrary was discovered  Damn it. Apparently the rear pads (or at least, the retaining clips) were not reinstalled correctly. This was fixed and the calipers cleaned and lubricated, most of the problems gone.

However, the rotors (and presumably, the pads) have glazed over, which explains the symptoms that remain. I suspect these were never properly bedded in. What's the best way of fixing this - can you just burn this off by giving the brakes a jolly good rogering, can you scrub the rotors and/or pads with something (ie sandpaper), or do you have to machine the rotors (and if so, is there anything that you can or must do to the pads)?

Cheers!
Rory

[L4OMEO]

Can't argue that Choderboy. We were pretty confident we had it done correctly but clearly not, a professional double-check would have been the wise move. Hindsight huh 

[wankski]

so we can assume in the absence of proof to the contrary, you did an excellent job!

Err ... unfortunately proof to the contrary was discovered   Damn it. Apparently the rear pads (or at least, the retaining clips) were not reinstalled correctly. This was fixed and the calipers cleaned and lubricated, most of the problems gone.

However, the rotors (and presumably, the pads) have glazed over, which explains the symptoms that remain. I suspect these were never properly bedded in. What's the best way of fixing this - can you just burn this off by giving the brakes a jolly good rogering, can you scrub the rotors and/or pads with something (ie sandpaper), or do you have to machine the rotors (and if so, is there anything that you can or must do to the pads)?

Cheers!
Rory

do'h... how was the clip not installed correctly?

glazing.. its hard to tell without seeing the glazing... At this point since everything is new I would go with the hard braking option and hope it goes away.

U never, ever use sandpaper. Use a metal file (as in one designed to file down metal). And you have to be quite gentle with its use and application (unidirectional, be totally square with the pad, and just enough to remove the smooth glazed over look)...

discs can be machined, but without looking at it I say don't. In the 2.5, u are running the same package as the 2.0. That is 22mm dics that can go down to min spec 20.2... Not much machining in that one...

Depending on what the pads have done to the disc, I'd just live with it, since swapping everything over again is unlikely to be met with a positive response from the 'minister of finance'...


oh well, cheer up, u guys mostly did a good job and besides...

can't remember who said it, but maybe your expereince is not meant to be an example, but rather to serve as a warning to others??    

[L4OMEO]

do'h... how was the clip not installed correctly?

Don't know. Can't even picture the damn thing at the moment.

glazing.. its hard to tell without seeing the glazing... At this point since everything is new I would go with the hard braking option and hope it goes away.

Yeah, I'll give that a crack and come back to your other advice if that doesn't work.

swapping everything over again is unlikely to be met with a positive response from the 'minister of finance'

'aint that the truth ...

maybe your experience is not meant to be an example, but rather to serve as a warning to others??   

In that case I'll happily accept donations from anyone who uses my experience to avoid doing things the expensive way 


Cheers
Rory